CRUSTACEA OF ALABAMA. 



17 



and internally three setae. The fifth foot consists of a fleshy basal segment, more or less 

 coalescent with the last thoracic segment and bearing a curved spine externally, and a 

 terete terminal segment .012 mm. long, which bears a seta four times its own length. 

 The abdomen is slender and its last segment bears.a series of spines above on the posterior 

 margin. The egg sacs are appressed and contain eight to twenty rather large ova. 

 The color is bronzy and opaque. 



Cyclops simplex, Poggenpoi. 



(Plate VII, Fig. 1.) 



Description of the Female. The form is very slender, an average individual measur- 

 ing between .95 and 1.00 mm. exclusive of the caudal setae. The following detailed 

 measurements of a specimen measuring .976 mm. will serve to exhibit the proportions of 

 the parts : First thoracic segment .30 mm., second segment .08 mm., third segment .08 

 mm., fourth segment .056 mm., fifth segment .024 mm.; first (apparent) abdominal segment 

 .16 mm., second segment .08 mm., third segment .048 mm.; caudal stylets .088 mm., 

 outer seta .08 mm., outer median .30 mm., inner median .46 mm., inner .20 mm., dorsal 

 .06 mm.; the lateral seta is .036 mm. from the end. The antennae reach nearly to the 

 base of the thorax when reflexed, and are quite strong. They resemble those of C. ten- 

 uicornis in several particulars, but since it is desirable to distinguish this species with the 

 greatest possible accuracy, the following numbers are given to express the relative length 

 of the several segments beginning with the first: (i)20, (2)5, (3)3, (4)10, (5)7, (6)4, 

 (7)11, (8)5, ( 9 )5, (io)5, (1 1)7, (i2)7, (i 3 )5, (14)6, (i 5 )10, (i6)15, (i 7 )14. The fourth, 

 eleventh, fourteenth and fifteenth segments bear the longest setae. The last two seg- 

 ments are armed with a knife-like ridge similar to that found in C. tenuicoruis , this ridge 

 is serrulated on the last segment and near the end is cut by a deep incision so that the 

 terminal part is like a hook notched upon its convex outer part. The antennules are 

 slender and but moderately spinous, the first three segments being almost exactly equal 

 (.06 mm.) while the terminal segment is as long as the basal segment of the antennae 

 (.08 mm.) The labrum is armed with thirteen small teeth. The larger maxilliped is 

 pearled on the posterior margin of its largest segment. The armature of the terminal 

 joints of the feet is as follows : 



f ex. 1 spine. C ex. 1 seta. 



I. Outer ramus -j ap. 1 spine, 1 seta; Inner ramus. < ap. 1 spine, 1 



( in. 3 setas. 



(in. 



seta. 



2 setas. 



f ex. 2 spine. f ex. 1 seta. 



II. and III. Outer ramus. < ap. 2 spines, 1 seta; Inner ramus. < ap. 1 spine, 1 setae, 

 (in. 3 setas. (in. 3 setas. 



( ex. 1 spine. f ex. 1 seta. 



IV. Outer ramus. ■< ap. 2 setas, 1 seta, Inner ramus. - ap. 2 spines. 

 (in. 3 setas. (in. 2 setas. 



